function J = Jaco(x, k, g11, g12, g21, g22)
    % 正确的解析雅可比矩阵
    J = [ ...
        -1 + g11*sech(x(1))^2 + k*cos(pi*x(3)),   g12*sech(x(2))^2,   -pi*k*sin(pi*x(3))*x(1);
         g21*sech(x(1))^2,                        -1 + g22*sech(x(2))^2, 0;
         1,                                       0,                   0 ...
    ];
end
